X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fcgroup_freezer.c;h=ce71ed53e88fbd1e648de49242d9fa63cc570685;hb=9b8eb4d14767209c83087063352cd04266ecdfd1;hp=5e6d26b66e88200206a584f3daf7a1c287247651;hpb=00c2e63c31d0f431952ff2a671c5c6997dd4f8b2;p=safe%2Fjmp%2Flinux-2.6

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 5e6d26b..ce71ed5 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -15,6 +15,7 @@
  */
 
 #include <linux/module.h>
+#include <linux/slab.h>
 #include <linux/cgroup.h>
 #include <linux/fs.h>
 #include <linux/uaccess.h>
@@ -47,17 +48,20 @@ static inline struct freezer *task_freezer(struct task_struct *task)
 			    struct freezer, css);
 }
 
-int cgroup_frozen(struct task_struct *task)
+int cgroup_freezing_or_frozen(struct task_struct *task)
 {
 	struct freezer *freezer;
 	enum freezer_state state;
 
 	task_lock(task);
 	freezer = task_freezer(task);
-	state = freezer->state;
+	if (!freezer->css.cgroup->parent)
+		state = CGROUP_THAWED; /* root cgroup can't be frozen */
+	else
+		state = freezer->state;
 	task_unlock(task);
 
-	return state == CGROUP_FROZEN;
+	return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
 }
 
 /*
@@ -85,10 +89,10 @@ struct cgroup_subsys freezer_subsys;
 
 /* Locks taken and their ordering
  * ------------------------------
- * css_set_lock
  * cgroup_mutex (AKA cgroup_lock)
- * task->alloc_lock (AKA task_lock)
  * freezer->lock
+ * css_set_lock
+ * task->alloc_lock (AKA task_lock)
  * task->sighand->siglock
  *
  * cgroup code forces css_set_lock to be taken before task->alloc_lock
@@ -96,33 +100,38 @@ struct cgroup_subsys freezer_subsys;
  * freezer_create(), freezer_destroy():
  * cgroup_mutex [ by cgroup core ]
  *
- * can_attach():
- * cgroup_mutex
+ * freezer_can_attach():
+ * cgroup_mutex (held by caller of can_attach)
  *
- * cgroup_frozen():
+ * cgroup_freezing_or_frozen():
  * task->alloc_lock (to get task's cgroup)
  *
  * freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
- * task->alloc_lock (to get task's cgroup)
  * freezer->lock
  *  sighand->siglock (if the cgroup is freezing)
  *
  * freezer_read():
  * cgroup_mutex
  *  freezer->lock
+ *   write_lock css_set_lock (cgroup iterator start)
+ *    task->alloc_lock
  *   read_lock css_set_lock (cgroup iterator start)
  *
  * freezer_write() (freeze):
  * cgroup_mutex
  *  freezer->lock
+ *   write_lock css_set_lock (cgroup iterator start)
+ *    task->alloc_lock
  *   read_lock css_set_lock (cgroup iterator start)
- *    sighand->siglock
+ *    sighand->siglock (fake signal delivery inside freeze_task())
  *
  * freezer_write() (unfreeze):
  * cgroup_mutex
  *  freezer->lock
+ *   write_lock css_set_lock (cgroup iterator start)
+ *    task->alloc_lock
  *   read_lock css_set_lock (cgroup iterator start)
- *    task->alloc_lock (to prevent races with freeze_task())
+ *    task->alloc_lock (inside thaw_process(), prevents race with refrigerator())
  *     sighand->siglock
  */
 static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
@@ -159,7 +168,7 @@ static bool is_task_frozen_enough(struct task_struct *task)
  */
 static int freezer_can_attach(struct cgroup_subsys *ss,
 			      struct cgroup *new_cgroup,
-			      struct task_struct *task)
+			      struct task_struct *task, bool threadgroup)
 {
 	struct freezer *freezer;
 
@@ -177,6 +186,19 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
 	if (freezer->state == CGROUP_FROZEN)
 		return -EBUSY;
 
+	if (threadgroup) {
+		struct task_struct *c;
+
+		rcu_read_lock();
+		list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
+			if (is_task_frozen_enough(c)) {
+				rcu_read_unlock();
+				return -EBUSY;
+			}
+		}
+		rcu_read_unlock();
+	}
+
 	return 0;
 }
 
@@ -184,9 +206,23 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 {
 	struct freezer *freezer;
 
-	task_lock(task);
+	/*
+	 * No lock is needed, since the task isn't on tasklist yet,
+	 * so it can't be moved to another cgroup, which means the
+	 * freezer won't be removed and will be valid during this
+	 * function call.  Nevertheless, apply RCU read-side critical
+	 * section to suppress RCU lockdep false positives.
+	 */
+	rcu_read_lock();
 	freezer = task_freezer(task);
-	task_unlock(task);
+	rcu_read_unlock();
+
+	/*
+	 * The root cgroup is non-freezable, so we can skip the
+	 * following check.
+	 */
+	if (!freezer->css.cgroup->parent)
+		return;
 
 	spin_lock_irq(&freezer->lock);
 	BUG_ON(freezer->state == CGROUP_FROZEN);
@@ -296,27 +332,22 @@ static int freezer_change_state(struct cgroup *cgroup,
 	int retval = 0;
 
 	freezer = cgroup_freezer(cgroup);
+
 	spin_lock_irq(&freezer->lock);
+
 	update_freezer_state(cgroup, freezer);
 	if (goal_state == freezer->state)
 		goto out;
-	switch (freezer->state) {
+
+	switch (goal_state) {
 	case CGROUP_THAWED:
-		retval = try_to_freeze_cgroup(cgroup, freezer);
+		unfreeze_cgroup(cgroup, freezer);
 		break;
-	case CGROUP_FREEZING:
-		if (goal_state == CGROUP_FROZEN) {
-			/* Userspace is retrying after
-			 * "/bin/echo FROZEN > freezer.state" returned -EBUSY */
-			retval = try_to_freeze_cgroup(cgroup, freezer);
-			break;
-		}
-		/* state == FREEZING and goal_state == THAWED, so unfreeze */
 	case CGROUP_FROZEN:
-		unfreeze_cgroup(cgroup, freezer);
+		retval = try_to_freeze_cgroup(cgroup, freezer);
 		break;
 	default:
-		break;
+		BUG();
 	}
 out:
 	spin_unlock_irq(&freezer->lock);
@@ -336,7 +367,7 @@ static int freezer_write(struct cgroup *cgroup,
 	else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
 		goal_state = CGROUP_FROZEN;
 	else
-		return -EIO;
+		return -EINVAL;
 
 	if (!cgroup_lock_live_group(cgroup))
 		return -ENODEV;
@@ -355,6 +386,8 @@ static struct cftype files[] = {
 
 static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
 {
+	if (!cgroup->parent)
+		return 0;
 	return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
 }